Toothed belt wheel with a collar

ABSTRACT

A cog belt pulley system includes cog belt pulleys ( 10   a  to  10   c ) each with at least one flange ( 15  to  17 ) protruding in the radial direction beyond the toothed circumferential surface ( 11 ) and extending in the circumferential direction to limit slipping of the belt ( 20, 30, 40 ) at right angles to the circumferential direction of the pulleys ( 10   a  to  10   c ). Said flange is provided only as a segment over a limited part of the circumferential surface in the circumferential direction of the pulleys. A belt is mounted on two pulleys by the pulleys being rotated into a position in which the particular flange segments face each other. In this position the belt can be pushed onto the pulleys without colliding with the flange segments.  
     This substantially facilitates mounting and replacement of the belts. No separate measures are required, such as removing the flange before pushing on the belt or separately pretensioning an overly long belt after its mounting. Thus, constructional and maintenance effort are reduced.

[0001] This invention relates to a cog belt pulley with at least one flange, the pulley having a toothed circumferential surface for engagement of one or more cog belts. The invention relates in addition to a cog belt pulley system having a plurality of such cog belt pulleys.

[0002] Cog belt pulley systems are used in machines for coupling a plurality of spaced apart axles by means of cog belts so that one motor suffices for driving all coupled axles. The drive of more than two axles can be guaranteed by one cog belt by guiding said belt over a corresponding number of cog belt pulleys. However, a separate cog belt can also be provided per axle pair (cascade arrangement).

[0003] The flange for in particular preventing the belt from laterally slipping off the cog belt pulley during operation is usually formed by a flanged wheel disposed on one or both faces of the cog belt pulley. U.S. Pat. No. 3,918,515 and FR 2 520 466 A also disclose forming the flanged wheels of individual segments, the segments being distributed over the total circumference of the cog belt pulley.

[0004] However, the presence of the flanged wheels poses a problem during mounting and replacement of cog belts. Since the mounted belt requires an at least small pretension to guarantee reliable engagement with the pulley in operation even at high loads and high speeds. It is not readily possible to lay the belt easily on preassembled cog belt pulleys over the flanged wheels. This problem can be avoided by mounting the flanged wheel only after laying the belt on the pulley, or by swiveling the pulley into the operating position and locking it only after laying on the belt, or by using a belt with overlength and pretensioning it by means of a separate tension roller only after mounting it. These solutions involve considerable constructional effort, however.

[0005] In particular in relatively complex machines, such as bank note processors, in which numerous axles are coupled in cascade arrangement via a plurality of cog belts, the constructional effort of the machine and the maintenance effort for changing belts become extremely great.

[0006] The problem of the present invention is therefore to propose a cog belt pulley and cog belt pulley system that both permit simple mounting of the belt and reliably prevent the belt from slipping off during operation.

[0007] This problem is solved according to the invention by means of a cog belt pulley and cog belt pulley system according to the independent claims.

[0008] Preferred embodiments of the invention are stated in claims dependent thereon.

[0009] To solve the problem it is proposed that the flange intended for preventing the belt from slipping off in operation be formed as a flange segment only over a limited part of the pulley circumference. When the pulleys of two axles to be coupled are rotated relative to each other so that the particular flange segments protruding beyond the pulley circumference face each other, the belt can be pushed onto the two pulleys over the flange segments without colliding with the flange segments.

[0010] This presupposes that the flange segment lengths in the circumferential direction of the pulleys are selected so that the flange segments are completely within the inside area of the belt, i.e. between load strand and return strand, when the belt is pushed on. At given angle of wrap α of a belt about a pulley, the flange segment can extend in the circumferential direction of the pulley over a clearance angle of 360° −α without collision occurring when the belt is pushed on. However, it must be heeded that the local radial height of the flange segment is adapted to the tangential course of the belt. In the case of equally large pulleys to be coupled, for example in connection with the drive of roller tracks, the flange segments should therefore extend over slightly less than 180° of the pulley circumference. However, if the diameters of two pulleys to be coupled are different (multiplication or reduction), the flange segment of the larger pulley extends over a smaller inscribed angle (for example 140°) than the flange segment of the smaller pulley (for example 220°).

[0011] The invention thus offers the essential advantage that all pulleys can be preassembled and can remain that way when the belt or belts are mounted or replaced in the course of maintenance.

[0012] In the case of relatively complex machines with a large number of axles driven by one motor and interconnected in cascade arrangement, wherein two axles at a time are thus coupled by a separate cog belt, the mounting of the belts is effected in simple fashion by bringing the flange segments of two pulleys in mutually opposing positions by rotating the associated axles and pushing the belt onto the pulleys past the flange segments. In this way the complete belt cascade can be mounted successively.

[0013] In the case of a belt cascade, at least two belts run on the middle axles of the cascade in each case. For such cases it is advantageous if three flange segments are provided, one flange segment between two belts and one flange segment on each side of the belts, that are mutually offset by 120° in the circumferential direction. A belt pushed onto the pulleys in the above-described way can be pushed further past the middle flange segment into the back position, that is, onto the back pulley, when the associated axle is rotated by 120°.

[0014] More than two belts can also run on one axle, whereby an accordingly larger number of flange segments distributed evenly over the circumference is to be provided. In the case of n belts, n flanged wheels (flanged wheel limiting on one side) or n+1 flanged wheels (flanged wheels limiting on both sides) are preferably provided that are mutually offset by 360°/n or 360°/(n+1) in the circumferential direction.

[0015] The invention is likewise employable in cog belt pulley systems in which one belt is guided over more than two pulleys.

[0016] According to a preferred embodiment of the invention, the flange segments are beveled toward the pulley. This ensures that the belts do not run onto a flange segment and slip or even break in operation, but are instead pushed back onto the pulley.

[0017] The inventive flanged cog belt pulley can be executed advantageously as an integral component, for example an injection molded part. Alternatively, the flange segment can be executed as a separate component that is mounted on the pulley, for example screwed on its face, or slipped onto the axle adjacent to the pulley.

[0018] The invention will be explained in the following by way of example with reference to the accompanying drawings, which indicate further advantages and aspects of the invention.

[0019]FIG. 1 shows in perspective an inventive cog belt pulley with integrated flange segments;

[0020]FIG. 2 shows a side view of the cog belt pulley according to FIG. 1;

[0021]FIG. 3 shows a side view of a cog belt pulley system in cascade arrangement according to the invention; and

[0022]FIG. 4 shows a perspective view of a cog belt pulley system in cascade arrangement according to the invention.

[0023]FIG. 4 shows a cog belt pulley system with three pulleys 10 a, 10 b, 10 c that are coupled in cascade arrangement over belts 20, 30, 40 by two pulleys 15 a, 15 b or 15 b, 15 c being driven over common belt 20 or 30 in each case.

[0024] Pulley 10 corresponding to pulleys 10 a to 10 c is shown in perspective in FIG. 1 and in a side view in FIG. 2. Pulley 10 has toothed circumferential surface 11 and flange segments 15, 16, 17 integrally formed on pulley 10 as well as central axle bore 12. It can be produced in this form as an integral component by injection molding.

[0025] Flange segments 15 to 17 rise in the radial direction beyond toothed circumferential surface 11 and prevent lateral displacement of the belts circulating on the pulley. Pulleys 10 shown in the figures are intended for circulation of two belts, with middle flange segment 16 serving as a spacer between the belts. Outer flange segments 15, 17 have the function of preventing the belt from slipping off toothed circumferential surface 11 during operation. Instead of one integral component, as shown in FIG. 1, the same pulley complex can also be realized by two separate pulleys separated from each other by a flange segment and equipped laterally with a further flange segment in each case.

[0026] The detail of pulley 10 shown enlarged in FIG. 2 shows in a detail an area between two teeth of toothed circumferential surface 11. At base 3 of the teeth groove 4 is provided that serves to reduce noise arising during operation of pulley 10 with a belt. Noise reduction is obtained by compressed air being able to escape via grooves 4. Compressed air arises during operation when the teeth of the belt and pulley 10 mesh.

[0027] In the case shown in FIG. 1 of pulley 10 intended for two belts and therefore having three flange segments 15 to 17, the flange segments are spaced apart by 120° over the circumference, as illustrated in FIG. 2. A reason for this is that uniform mass distribution should preferably avoid balance errors. Accordingly, an angular spacing of the flange segments of 360°/n over the pulley circumference results quite generally for a pulley with n flange segments. The angular spacing also results from the one-sided mounting of belts located one behind the other as described below.

[0028]FIG. 3 shows a side view of a pulley system with cascade coupling. That is, two belts 20, 30 or 30, 40 run on each axle and there are accordingly three flange segments 15 b to 17 b or 15 c to 17 c for each axle that are associated with pulleys 10 b and 10 c. The root diameter is identical for both pulleys 10 b, 10 c so that load strand and return strand of belt 30 extend parallel to each other. Flange segments 15 b and 15 c extend starting out from the root circle of pulley 10 so as to be capable of being guided between load strand and return strand of belt 30. That is, flange segments 15 b and 15 c extend over somewhat less than 18020 of the root circle of pulley 10 b or 10 c. In the embodiment shown in FIG. 3, the area where belt 30 is not guided laterally by any of flange segments 15 b and 15 c includes only about 2 to 3°.

[0029] Mounting belt 30 on pulleys 10 b and 10 c is very simple due to the special design of flange segments 15 b, 15 c. Before belt 30 is pushed laterally onto pulleys 10 b, 10 c, pulleys 10 b, 10 c are rotated into the position shown in FIG. 3 where their outer flange segments 15 b, 15 c face each other so that the flange segments lie between load strand and return strand of belt 30. It is then readily possible to push belt 30 past flange segments 15 b, 15 c. In operation, that is, when pulleys 10 b, 10 c are rotating, the belt is guided laterally by flange segments 15 b, 15 c virtually continuously, apart from a negligibly small area of about 2 to 3°. In order to prevent belt 30 from running onto flange flange segments 15 b, 15 c during this short time period, the inside flanks of flange segments 15 b, 15 c slope toward toothed circumferential surface 11 (not shown). This ensures that belt 30, should it slip, is pushed back onto the pulley.

[0030] The pulley systems are normally only accessible on one side, so that the belts are pushed onto the pulleys one after the other, beginning with the rearmost belt. This will be explained in the following with reference to FIG. 4.

[0031] First, belts 20 and 40 are pushed onto pulleys 10 a, 10 b and 10 c. In the case of belt 40 this is done in a position of pulley 10 c as shown in FIG. 4. Belt 20 is also first pushed onto pulleys 10 a, 10 b in the position in which pulleys 10 a, 10 b are shown in FIG. 4, that is, with outer flange segments 15 a, 15 b facing inside or each other. Pulley 10 b is then rotated counterclockwise by 120° so that middle flange segment 16 b now faces inside. Simultaneously, pulley 10 a likewise rotates counterclockwise due to the pulley coupling, so that associated middle flange segment 15 b, which is not visible in the perspective view of FIG. 4, likewise faces inside and is opposite flange segment 16 b. In this state, belt 20 can be pushed over middle flange segments 16 a, 16 b into the back position as shown in FIG. 4. Finally, belt 30 is mounted by rotating hitherto uncoupled pulleys 10 b and 10 c so that their outer flange segments 15 b, 15 c face each other (as shown in FIG. 3; rotated by 180° in each case over the position shown in FIG. 4). Belt 30 can then be easily pushed on, thereby completing the cascade pulley system.

[0032] Besides the shown pulley for two belts, pulleys with flange segments can also be designed for one or more than two belts. If the pulley is used for more than two belts, it may be helpful for mounting to reduce the size of the flange segments in the circumferential direction.

[0033] The rearmost flange in terms of mounting can be designed as a complete flanged wheel, since the belt is usually not pushed beyond this position.

[0034] The inventive cog belt pulleys can also be used in gear systems in which a cog belt is guided over more than two pulleys. The size of the flange segments in the circumferential direction can then be enlarged. 

1. A cog belt pulley (10) having at least one flange(15, 16, 17), the pulley (10) having a toothed circumferential surface (11) for engagement of one or more cog belts (20, 30, 40) and the flange protruding radially beyond the toothed circumferential surface (11) in the circumferential direction of the pulley (10) to limit slipping of the belt (20, 30, 40) at right angles to the circumferential direction of the pulley (10), characterized in that at least one flange is designed as a flange segment (15, 16, 17), each flange extending only over a limited part of the pulley circumference such that when one of the belts (20, 30, 40) is pushed onto the pulley (10) there is no collision with the flange.
 2. A cog belt pulley according to claim 1, characterized in that each flange extends over less than 180° of the pulley circumference.
 3. A cog belt pulley according to claim 1 or 2, characterized in that the flange segment (15, 16, 17) is beveled to slope toward the toothed circumferential surface (11).
 4. A cog belt pulley according to any of claims 1 to 3, characterized in that at least two flange segments (15, 17) with an intermediate toothed circumferential surface (11) are provided.
 5. A cog belt pulley according to any of claims 1 to 4, characterized in that at least three flange segments (15, 16, 17} with an intermediate toothed circumferential surfaces (11) are provided.
 6. A cog belt pulley according to claim 5, characterized in that the flange segments (15, 16, 17) are mutually offset by 120° in the circumferential direction.
 7. A cog belt pulley according to any of claims 1 to 6, characterized in that the cog belt pulley (10) and the at least one flange segment (15, 16, 17) are formed as an integral component.
 8. A cog belt pulley according to claim 7, characterized in that the integral component is an injection molded part.
 9. A cog belt pulley according to any of claims 1 to 6, characterized in that the at least one flange segment (15, 16, 17) is formed as an independent component.
 10. A cog belt pulley according to any of claims 1 to 9, characterized in that a depression (4), in particular a groove, is formed at the base (3) of each tooth of the cog belt pulley (10).
 11. A cog belt pulley system comprising at least two axles each with at least one cog belt pulley according to any of claims 1 to 9, whereby two flange segments (15 a, 15 b or 15 b, 15 c) of pulleys (10 a, 10 b or 10 b, 10 c) coupled via a cog belt (20 or 30) face each other in a certain axle angle position such that the belt (20 or 30) can be pushed past the segments (15 a, 15 b or 15 b, 15 c) at right angles to the circumferential direction of the pulleys (10 a, 10 b or 10 b, 10 c).
 12. A cog belt pulley system according to claim 11, characterized in that four or more flange segments with intermediate toothed circumferential surfaces (11) are disposed on one axle.
 13. A cog belt pulley system according to claim 11 or 12, characterized in that one belt is guided over three or more pulleys. 